Setup test options in the UI

[jaaydenh]

1. Add dropdowns to set the testdata folder
2. Add dropdown set a test user by setting the user query param, the set of test users is retrieved from /users/{dir}
3. Add a switch to turn on/off using the plan path
4. Explicitly close and reopen the websocket connection after changing any of these settings

[Kira-Pilot]

@jaaydenh Can you cleanup the description here so it's clear what this ticket calls for (or close this out if it isn't relevant anymore)? I've removed you as an assignee because I don't think you're actively working on it; however please add yourself back if I'm incorrect!

[jaaydenh]

@Kira-Pilot not sure why I put this in coder/internal instead of coder/preview, buts its been completed already so I can close it.